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Discussion Starter · #1 ·
hea all new to this forum.. 04 sportsman 500 ho i cannot figure out wut is wrong with my bike,, here is the problem, at about 1/2 throttle the engine will miss/ cut out. loses power and just will not run right, sometimes it does it all the time some times it runs fine.... now here is wut i have done to it...new spark plug(many times) new coil, rebuilt fuel pump, new carb, new air filter, adjust valves to spec, check mechanical timing and electronic timing, rebuilt drive clutch, new belt, all new fuel lines from tank, this is driving me nuts,,,,,,dosent matter if its hot, cold, wet, dry,,this prob is always there can anyone help????
 

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Boy that has me scratching my head!:stupido:
 

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Check the cam, the lobs, at one time there was a batch of soft cams, the exhaust lobs can wear down or completly off. you can also take a timming light and shine into the carb when running and see if it is spitting fuel out. I had a fruit force that both cams were wore slap out.
 

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Discussion Starter · #5 ·
hea guys thankx. but i have had the valve cover off and inspected the whole top end,,, no metal in the oil or it would show up on the mag in the oil tank drain and no visible defects on the cam itself... could it be in the cdi box?? or possibly the pulse coil??? n e thoughts
 

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stumped

thats a good ???? i guess you could have a intermitent prob with one or the other. wont be long and you will have a old frame and all new parts. sorry i cant fig this one out.
 

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I found this thread a little bit late. Have you solved the issue yet?

I am having a similar problem on my 2002 Sportsman 400. It has been getting worse. I had suspected the cam but am still in denial.:nervous:.

So far I have checked the plug fuel filter and carb. My next check will be the top end.

I'll let you know if I stumble across anything.
 

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Did anyone tell you to adjust the throttle cable? I had the 04.5 sportsman doesn't matter all polaris atv's are equiped with a safety on the throttle so if the cable has a greater amount of slack it is designed to cut out ignition or make your atv powerless. I know it might sound stupid but this happened to me and the only reason why we knew how to fix this problem is because it happened to us on my buddies 600 polaris the weekend before. Goodluck man.
 

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I have seen two different results for this same issue on my buddies bike one we found that the ground was loose cleaned it and retightened it and it fixed the problem. The second one was the CDI cox sending reverse gear code while driving in High but would not do it in Low
 

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I seem to have fixed the Sportsman 400. The problem seemed to be somewhat intermittent so I was leaning towards ignition. The backfire was severe sometimes and I had a thought that it might be a sticking valve.

I put an ounce of 2 cycle oil into the gas tank and ran it for about 1/2 hour then let it sit overnight. Came home the next day and the problem is gone. Runs like a top.

Who knows, it might come back and still could be ignition but at least I know the cam is OK.
 
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